Laser oscillator

ABSTRACT

The present invention provides a laser oscillator using an electroluminescent material that can enhance directivity of emitted laser light and resistance to a physical impact. The laser oscillator has a first layer including a concave portion, a second layer formed over the first layer to cover the concave portion, and a light emitting element formed over the second layer to overlap the concave portion, wherein the second layer is planarized, an axis of laser light obtained from the light emitting element intersects with a planarized surface of the second layer, the first layer has a curved surface in the concave portion, and a refractive index of the first layer is lower than that of the second layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laser oscillator using anelectroluminescent material that can emit laser light.

2. Description of the Related Art

A semiconductor laser has a merit that a laser oscillator can beminiaturized and reduced in weight drastically, as compared with a gasor solid-state laser. Thus, a semiconductor laser comes into practicaluse in various fields, as a light-source for receiving and transmittinga signal by an optical interconnection in an optical integrated circuit,a light-source for recording in a recording medium such as an opticaldisk or an optical memory, and a light-source for optical communicationsusing fiber-optics or the like as a light guide. The oscillationwavelength of a semiconductor laser has a wide range of from the bluewavelength to the infrared wavelength. Many semiconductor lasers thatare used generally have their oscillation wavelengths in an infraredregion, for example, the wavelength of a GaAs laser is 0.84 μm, thewavelength of an InAs laser is 3.11 μm, the wavelength of an InSb laseris 5.2 μm, the wavelength of a GaAlAs laser is 0.72 to 0.9 μm, and thewavelength of an InGaAsP laser is 1.0 to 1.7 μm.

In recent years, many researches on a practical use of a semiconductorlaser having the oscillation wavelength in a visible region have beenmade. Depending on the trend, a laser oscillator that can emit laserlight by using an electroluminescent material that can produceelectroluminescence by being applied with an electric field (an organicsemiconductor laser) has attracted more attentions. An organicsemiconductor laser is expected to have a variety of use, since theorganic semiconductor laser can emit laser light whose wavelength is ina visible region and it can be formed over an inexpensive glasssubstrate.

Reference 1 describes an organic semiconductor laser of which peakwavelength λ is 510 nm (Reference 1: Japanese Patent Laid Open No.2000-156536. p. 11).

Laser light emitted from an organic semiconductor laser is generallylower in the directivity and tend to diffuse than other lasers. When thedirectivity of laser light is low, receiving and transmitting a signalin an optical interconnection becomes unstable due to disclination, andthus, high integration of an optical integrated circuit is prevented,which is not preferable. When divergence of laser light is large, it isdifficult to assure the energy density of the laser light. A desiredenergy density can be assured by enhancing the intensity of laser lightemitted from a light-source or by shortening the distance between alight-source of laser light and a predetermined region. However, theformer has a demerit of increasing power consumption and the latter hasa demerit of limits on use of the organic semiconductor laser.

The directivity of laser light can be enhanced by providing an opticalsystem prepared separately for an organic semiconductor laser that is alight-source. However, as the optical system is more complicated, anadjustment of the optical system in maintenance or positioning of theoptical system and the organic semiconductor laser is more troublesome.Further, resistance to a physical impact also becomes worse.

SUMMARY OF THE INVENTION

In view of the above mentioned problems, it is an object of the presentinvention to provide a laser oscillator using an electroluminescentmaterial that can enhance directivity of emitted laser light andresistance to a physical impact.

The present inventors have conceived that directivity of laser lightobtained by a light-emitting element can be enhanced by giving afunction as an optical system to a substrate supporting thelight-emitting element using an electroluminescent material, a layersuch as a base film or a layer covering the light-emitting element.

Specifically, a laser oscillator of the present invention has a firstlayer including a concave portion, a second layer formed over the firstlayer to cover the concave portion, and a light emitting element formedover the second layer to overlap the concave portion, wherein the secondlayer is planarized, an axis of laser light obtained from the lightemitting element intersects with a planarized surface of the secondlayer, the first layer has a curved surface in the concave portion, anda refractive index of the first layer is lower than that of the secondlayer.

The light-emitting element includes a first electrode (an anode), asecond electrode (a cathode) and a light emitting layer provided betweenthe two electrodes, and an electroluminescent material included in thelight emitting layer functions as a laser medium according to thepresent invention. Note that a hole injecting layer, a hole transportinglayer or the like between the light emitting layer and the anode, and anelectron injecting layer, an electron transporting layer or the likebetween the light emitting layer and the cathode, may be provided,respectively. In this case, all layers that are provided between theanode and the cathode are referred to as an electroluminescent layer, inwhich a light emitting layer is also included therein. In some cases, aninorganic compound is included in a layer for forming theelectroluminescent layer.

In addition, an optical resonator of the laser oscillator of the presentinvention is a plane-parallel type, for which two reflectors having aplane for reflecting and oscillating light are used. Specifically, apart of the first electrode and the second electrode is used as thereflector to form the optical resonator. However, a part of the firstelectrode and the second electrode is not necessarily used as thereflector for forming the optical resonator. For example, a film formedseparately to reflect light (reflective film) may be employed as thereflector. Alternatively, light generated in the light emitting layermay be reflected from a layer other than the light emitting layer, forexample, a hole injecting layer, a hole transporting layer, an electroninjecting layer, an electron transporting layer or the like, to form anoptical resonator.

In addition, the laser oscillator of the present invention does notnecessarily require the first layer having the concave portion. Forexample, the laser oscillator may have a light emitting element formedover the first layer, a second layer formed to cover the light emittingelement, in which the second layer may have a convex portion to overlapwith the light emitting element, a light axis of laser light obtainedfrom the light emitting element may intersect with the second layer, andthe second layer may have a curved surface in the convex portion.

Further, a concave portion and a convex portion may be formed to faceeach other with the light emitting element therebetween. In any case,the concave portion and the convex portion each have their center ofcurvature on the light emitting element side.

In the present invention, directivity of laser light emitted from anoptical resonator can be enhanced by a concave portion included in alayer for supporting a light emitting element or a convex portionincluded in a layer covering a light emitting element. Further,troublesome steps such as an adjustment of an optical system inmaintenance or positioning of the optical system and an organicsemiconductor laser can be prevented and the resistance to a physicalimpact can be enhanced since one part of the layer functions as anoptical system, which is different from the case of providing an opticalsystem separately.

These and other objects, features and advantages of the presentinvention become more apparent upon reading of the following detaileddescription along with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are a cross-sectional view and a top view of a laseroscillator, respectively according to one aspect of the presentinvention;

FIG. 2 is a cross-sectional view of a laser oscillator according to oneaspect of the present invention;

FIGS. 3A and 3B are cross-sectional views of a laser oscillatoraccording to one aspect of the present invention;

FIGS. 4A and 4B are cross-sectional views of a laser oscillatoraccording to one aspect of the present invention;

FIG. 5 shows a structure of a light-emitting element included in a laseroscillator according to one aspect of the present invention;

FIGS. 6A and 6B are a top view and a cross-sectional view in a processfor manufacturing a laser oscillator, respectively according to oneaspect of the present invention;

FIGS. 7A and 7B are a top view and a cross-sectional view of a laseroscillator, respectively according to one aspect of the presentinvention;

FIG. 8 is a cross-sectional view of a laser oscillator according to oneaspect of the present invention;

FIGS. 9A to 9C each show an embodiment for a method for manufacturing aconcave portion;

FIGS. 10A to 10F each show an embodiment for a method for manufacturinga concave portion;

FIG. 11 shows an embodiment for a method for manufacturing a convexportion;

FIGS. 12A to 12C each show a structure of a laser pointer employing alaser oscillator according to one aspect of the present invention;

FIG. 13 shows a structure of a light-emitting element included in alaser oscillator according to one aspect of the present invention; and

FIG. 14 shows a positional relationship of a laser light-source and aconcave portion.

DETAILED DESCRIPTION OF THE INVENTION Embodiment Mode

One mode of a laser oscillator of the present invention is explainedwith reference to FIGS. 1A and 1B. FIG. 1A is a cross-sectional view ofthe laser oscillator of the present invention. FIG. 1B is a top view ofthe laser oscillator of the present invention shown in FIG. 1A. FIG. 1Ais a cross-sectional view taken along the line A-A′ of FIG. 1B. As shownin FIGS. 1A and 1B, the laser oscillator of the present inventionincludes a first layer 101 having a concave portion 100, and a secondlayer 102 formed over the first layer 101 to cover the concave portion100. The second layer 102 is formed to have a thickness enough to fillthe concave portion 100. The refractive index of the first layer 101 islower than that of the second layer 102. The second layer 102 islight-transmitting.

FIG. 1A shows an example that each of the first layer 101 and the secondlayer 102 is formed from one layer. Alternatively, each of these layersmay be formed from a plurality of layers. In this case, a layer of thefirst layer 101 that is closest to the second layer 102 is formed tohave lower refractive index than that of a layer of the second layer 102that is closest to the first layer 101.

As shown in FIGS. 1A and 1B, a light-emitting element 103 is formed overthe second layer 102 to overlap the concave portion 100. Thelight-emitting element 103 includes two electrodes 104 and 105, and anelectroluminescent layer 106 interposed between these electrodes 104 and105. One of the electrodes 104 and 105 is an anode, and the other is acathode. FIGS. 1A and 1B show an example that the electrode 104 servesas an anode, and the electrode 105 serves as a cathode. Alternatively,the electrode 104 may serve as a cathode, and the electrode 105 mayserve as an anode. Current is supplied to the electroluminescent layer106 by applying a forward bias voltage to the electrodes 104 and 105,thereby making the electroluminescent layer 106 emit light.

The first layer 101 has a curved surface in the concave portion 100. Thecenter of curvature of the curved surface is on the light emittingelement 103 side, that is, a distance of the first layer 101 to thecenter of curvature is longer than that of the first layer 101 to thelight emitting element 103.

In the laser oscillator shown in FIGS. 1A and 1B, an optical resonatoris formed by the electrodes 104 and 105 included in the light-emittingelement 103. Light generated in the electroluminescent layer 106 isoscillated by the electrodes 104 and 105, and is emitted as laser light.In the optical resonator, an optical axis of the emitted laser lightintersects with the second layer 102 and the emitted laser light isdirected to the first layer 101.

FIG. 2 shows the laser oscillator shown in FIGS. 1A and 1B, in which aforward bias voltage is applied to the electrodes 104 and 105. As shownby the arrows of broken lines, laser light is emitted toward the concaveportion 100 of the first layer 101 from the electrode 104 side byapplying voltage to the electrodes 104 and 105. The emitted laser lightdiverges to some extent, but the directivity is enhanced whilesuppressing the divergence angle by reflecting and converging the laserlight in the concave portion 100. The focus length of the concaveportion 100 may be optically designed in accordance with the divergenceangle of laser light emitted to the concave portion 100 so as tosuppress the divergence angle.

The mode of enhancing the directivity of laser light by reflecting andconverging the emitted laser light in the concave portion is describedin FIGS. 1A and 1B, and FIG. 2. However, the directivity of laser lightmay be enhanced by refracting and converging the light in the convexportion. A mode of a laser oscillator of the present invention that canenhance the directivity of laser light by refracting and converging thelight in the convex portion is described with reference to FIGS. 3A and3B.

FIG. 3A is a cross-sectional view of a laser oscillator of the presentinvention. The laser oscillator of the present invention includes afirst layer 200, a light emitting element 201 formed over the firstlayer 200, and a second layer 202 formed to cover the light emittingelement 201, as shown in FIG. 3A. The second layer 202 islight-transmitting and have a convex portion 203 to overlap the lightemitting element 201.

FIG. 3A shows an example in which the first layer 200 and the secondlayer 202 are each formed from one layer, but they may be each formedfrom plural layers.

The second layer 202 has a curved surface in the convex portion 203. Thecenter of curvature of the curved surface is on the light emittingelement 201 side, that is, a distance of the second layer 202 to thecenter of curvature is longer than that of the second layer 202 to thelight emitting element 201.

The light-emitting element 201 has two electrodes 204 and 205 and anelectroluminescent layer 206 interposed between the two electrodes 204and 205. Note that one electrode of the electrodes 204 and 205 is ananode and the other is a cathode. FIGS. 3A and 3B each show an examplein which the electrode 204 is an anode and the electrode 205 is acathode, but the electrode 204 may be a cathode and the electrode 205may be an anode. Current is supplied to the electroluminescent layer 206by applying a forward bias voltage to the electrodes 204 and 205,thereby making the electroluminescent layer 206 emit light.

In the laser oscillator shown in FIG. 3A, an optical resonator is formedby the electrodes 204 and 205 included in the light-emitting element201, like the laser oscillator shown in FIGS. 1A and 1B. The lightemitted from the electroluminescent layer 206 is oscillated by theelectrodes 204 and 205 to be emitted as laser light. The opticalresonator is formed in such a way that the optical axis of the emittedlaser light intersects with the second layer 202 and the emitted laserlight is directed to the second layer 202.

FIG. 3B shows a mode that a forward bias voltage is applied to theelectrodes 204 and 205 in the laser oscillator shown in FIG. 3A. Asshown by the arrows of broken lines, laser light is emitted toward theconvex portion 203 of the second layer 202 from the electrode 205 sideby applying voltage to the electrodes 204 and 205. The emitted laserlight diverges to some extent, but the directivity is enhanced whilesuppressing the divergence angle by refracting and converging the laserlight in the convex portion 203. The focus length of the convex portion203 may be optically designed in accordance with the divergence angle ofthe laser light emitted to the convex portion 203 so as to suppress thedivergence angle.

Moreover, a laser oscillator of the present invention may be formed sothat a concave portion for reflecting and converging laser light faces aconvex portion for refracting and converging laser light with alight-emitting element therebetween. A mode of the laser oscillator ofthe present invention, in which the concave portion faces the convexportion, is described with reference to FIGS. 4A and 4B.

FIG. 4A is a cross-sectional view of a laser oscillator of the presentinvention. As shown in FIG. 4A, the laser oscillator of the presentinvention includes a first layer 301 having a concave portion 300, and asecond layer 302 formed over the first layer 301 to cover the concaveportion 300. The second layer 302 is formed to have a thickness enoughto fill the concave portion 300. The refractive index of the first layer301 is lower than that of the second layer 302. The second layer 302 islight-transmitting.

FIG. 4A shows an example that each of the first layer 301 and the secondlayer 302 is formed from one layer. Alternatively, each of these layersmay be formed from a plurality of layers. In this case, a layer of thefirst layer 301 that is closest to the second layer 302 is formed tohave lower refractive index than that of a layer of the second layer 302that is closest to the first layer 301.

As shown in FIG. 4A, a light-emitting element 303 is formed over theplanarized second layer 302 to overlap the concave portion 300. A thirdlayer 304 is formed to cover the light emitting element 303. Thelight-emitting element 303 includes two electrodes 305 and 306 and anelectroluminescent layer 307 interposed between these electrodes 305 and306. Note that one electrode of the electrodes 305 and 306 is an anodeand the other is a cathode. FIG. 4A shows an example in which theelectrode 305 is an anode and the electrode 306 is a cathode, but theelectrode 305 may be a cathode and the electrode 306 may be an anode.Current is supplied to the electroluminescent layer 307 by applying aforward bias voltage to the electrodes 305 and 306, thereby making theelectroluminescent layer 307 emit light.

The third layer 304 is light-transmitting, and have a convex portion 308to overlap the light emitting element 303.

The first layer 301 has a curved surface in the concave portion 300. Thecenter of curvature of the curved surface is on the light emittingelement 303 side, that is, a distance of the first layer 301 to thecenter of curvature is longer than that of the first layer 301 to thelight emitting element 303. The third layer 304 has a curved surface inthe convex portion 308. The center of curvature of the curved surface ison the light emitting element 303 side, that is, a distance of the thirdlayer 304 to the center of curvature is longer than that of the thirdlayer 304 to the light emitting element 303.

FIG. 4A shows an example in which the third layer 304 is formed from onelayer, but may be formed from plural layers.

In the laser oscillator shown in FIG. 4A, an optical resonator is formedby the electrodes 305 and 306 included in the light-emitting element303. Light generated in the electroluminescent layer 307 is oscillatedby the electrodes 305 and 306 to be emitted as laser light. In theoptical resonator, an optical axis of the emitted laser light intersectswith the second layer 302 and the emitted laser light is directed to thefirst layer 301.

FIG. 4B shows the laser oscillator shown in FIG. 4A in which a forwardbias voltage is applied to the electrodes 305 and 306. As shown by thearrows of broken lines, laser light is emitted toward the concaveportion 300 of the first layer 301 from the electrode 305 side byapplying voltage to the electrodes 305 and 306. The emitted laser lightdiverges to some extent, but the directivity is enhanced whilesuppressing the divergence angle by reflecting and converging the laserlight in the concave portion 300. The focus length of the concaveportion 300 may be optically designed in accordance with the divergenceangle of laser light emitted to the concave portion 300 so as tosuppress the divergence angle. In the laser oscillator shown in FIGS. 4Aand 4B, the light reflected by the concave portion 300 can be convergedin the convex portion 308 of the third layer 304.

The convex portion 308 may be formed by a droplet discharging method asshown in FIG. 11 after forming the third layer 304. The referencenumerals 300 to 308 shown in FIG. 11 are equivalent to those of FIGS. 4Aand 4B. The reference numeral 309 denotes a nozzle of a dropletdischarging apparatus. A material that is a polymeric (high molecularweight) material and is transparent to light to be used, particularly,visible light, and that a solid polymeric material heated at equal to ormore than a melting point at a room temperature is preferably used asthe material which can be employed in forming the convex portion 308.For example, poly(alkylacrylate), poly(alkylmethacrylate), polystyrene,polyethylene, polypropylene, polycarbonate, a derivative thereof, andthe like can be used. In addition, a material formed by applying amonomer that is a raw material of the polymers and curing it by heatingof light-irradiation may be used.

As mentioned earlier, the directivity of laser light emitted from anoptical resonator can be enhanced by the concave portion included in thelayer for supporting the light emitting element or the convex portionincluded in the layer covering the light emitting element, according tothe present invention. Further, the resistance to a physical impact canbe enhanced since one part of the layer functions as an optical system,which is different from the case of providing an optical systemseparately.

In the laser oscillator shown in FIGS. 1A, 1B, 2, 3A, 3B, 4A and 4B,light is oscillated between two electrodes included in the lightemitting element, but the present invention is not limited thereto.Light may be oscillated by a reflective film prepared separately, orlight generated in the light emitting layer may be reflected from alayer other than the light emitting layer, for example, a hole injectinglayer, a hole transporting layer, an electron injecting layer, anelectron transporting layer or the like, to form an optical resonator.

Embodiment 1

A structure of a light-emitting element used for a laser oscillator ofthe present invention is explained in Embodiment 1.

FIG. 5 shows one mode of a structure of a light-emitting element used inthe present invention. A light-emitting element shown in FIG. 5 has astructure in which an electroluminescent layer 408 is included betweenan anode 401 and a cathode 407. The electroluminescent layer 408 isformed by sequentially stacking a hole injecting layer 402, a holetransporting layer 403, a light-emitting layer 404, an electrontransporting layer 405, and an electron injecting layer 406 over theanode 401.

A light-emitting element used for a laser oscillator of the presentinvention may include at least a light-emitting layer within anelectroluminescent layer. Layers having properties other than lightemission (a hole injecting layer, a hole transporting layer, an electrontransporting layer, and an electron injecting layer) can be combinedappropriately. Although not limited to the materials recited herein, theabove-mentioned layers are each formed by the following materials.

As the anode 401, a conductive material having a large work function ispreferably used. In the case that light is passed through the anode 401,a material having favorable light-transmitting properties is used forthe anode. 401. In this instance, a transparent conductive material suchas an indium tin oxide (ITO), an indium zinc oxide (IZO), or an indiumtin oxide containing silicon oxide (ITSO) may be used. In the case wherethe anode 401 is used as a reflector, a material that haslight-reflecting properties is used for the anode 401. For example,structures which are shown as follows can be used: a single layer ofcomprising one or plurality of elements selected from TiN, ZrN, Ti, W,Ni, Pt, Cr, Ag, or the like; a lamination layer of a film comprisingtitanium nitride film and a film mainly containing aluminum; and alamination structure of a triple film having a titanium nitride film, afilm comprising aluminum as its main component, and a film comprisingtitanium nitride. Alternatively, a lamination formed by stacking thetransparent conductive material on such a material that can reflectlight may be used as the anode 401.

As a hole injecting material for the hole injecting layer 402, amaterial that has comparative small ionization potential and smallvisible light absorption properties is preferably used. Such materialscan be broadly divided into metal oxides, low molecular organiccompounds, and high molecular organic compounds. Metal oxides such as avanadium oxide, a molybdenum oxide, a ruthenium oxide, and an aluminumoxide can be used. Low molecular organic compounds such as star-burstamine as typified by m-MTDATA, metallophthalocyanine as typified bycopper phthalocyanine (Cu-Pc), phthalocyanine (H₂-Pc), and2,3-dioxyethylenethiopehen derivatives can be used. The hole injectinglayer 402 may be formed by co-evaporation of the low molecular organiccompound and the metal oxide. High molecular organic compounds such aspolyaniline (PAni), polyvinyl carbazole (PVK), and polythiophenederivatives can be used. Polyethylenedioxythiophene (PEDOT), which isone of polythiophene derivatives, doped with polystyrene sulfonate (PSS)can be used.

As a hole transporting material for the hole transporting layer 403, aknown material that has favorable hole transporting properties and lowcrystallinity can be used. Aromatic amine (namely, a compound having abenzene ring-nitrogen bond) based compounds are preferably used. Forexample, 4,4-bis[N-(3-methylphenyl)-N-phenylamino]-biphenyl (TPD), andderivatives thereof such as4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (α-NPB) etc., arecited. Star burst aromatic amine compounds such as4,4′,4″-tris(N,N-diphenylamino)-triphenyl amine (TDATA), and MTDATA canbe also used. Alternatively, 4,4′,4″tris(N-carbazolyl)triphenylamine(TCTA) may be used. As a high molecular material, poly(vinylcarbazole)having favorable hole transporting properties can be used. Further,inorganic substances such as MoO_(x) can be used.

A known material can be used for the light-emitting layer 404. Forexample, metal complexes such as tris(8-quinolinolate) aluminum (Alq₃),tris(4-methyl-8-quinolinolate)aluminum (Almq₃),bis(10-hydroxybenzo[η]-quinolinato)beryllium (BeBq₂),bis(2-methyl-8-quinolinolato)-(4-hydroxy-biphenylyl)-aluminum (BAlq),bis[2-(2-hydroxyphenyl)-benzooxazolate]zinc (Zn(BOX)₂), orbis[2-(2-hydroxyphenyl)-benzothiazolate]zinc (Zn(BTZ)₂) can be used.Various fluorescent dyes (coumarin derivatives, quinacridonederivatives, rubrene, 4,4-dicyanomethylene, 1-pyron derivatives,stilbene derivatives, various condensation aromatic compounds, or thelike) can be also used. Phosphorescent materials such as platinumoctaethylporphyrin complexes, tris(phenylpyridine)iridium complexes, andtris(benzylideneacetonato)phenanthrene europium complexes can be used.Especially, phosphorescent materials have longer excitation time thanfluorescent materials, and thus the phosphorescent materials can makeeasily population inversion that is indispensable to laser oscillation,that is, the state where the number of molecules in an excited state islarger than that in a ground state. The foregoing materials can be usedas a dopant or a single layer film.

As a host material for the light-emitting layer 404, a hole transportingmaterial or an electron transporting material as typified by theforegoing examples can be used. A bipolar material such as4,4′-N,N′-dicarbazolyl-biphenyl (CBP) can be also used.

As an electron transporting material for the electron transporting layer405, metal complexes as typified by Alg₃ having a quinoline skeleton ora benzoquinoline skeleton, the mixed ligand complexes or the like can beused. Specifically, metal complexes such as Alq₃, Almq₃, BeBq₂, BAlq,Zn(BOX)₂, or Zn(BTZ)₂ can be cited. Alternatively, oxadiazolederivatives such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), or1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (OXD-7);triazole derivatives such as3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole (TAZ),or3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(p-EtTAZ); imidazole derivatives such as TPBI; phenanthrolinederivatives such as bathophenanthroline (BPhen); bathocuproin (BCP) inaddition to metal complexes can be used.

As an electron injecting material for the electron injecting layer, theforegoing electron transporting material can be used. Besides, an ultrathin film of insulator, for example, alkali metal halides such as LiF orCsF, alkali earth metal halides such as CaF₂, alkali metal oxides suchas LiO₂ is frequently used. Further, alkali metal complexes such aslithium acetylacetonate (Li(acac)) or 8-quinolinolato-lithium (Liq) canbe effectively used.

For the cathode 407, metals, alloys, electric conductive compounds thateach have a small work function, or a mixture thereof can be used.Specifically, alkali metals such as Li and Cs; alkali earth metals suchas Mg, Ca, and Sr; an alloy including the elements (Mg:Ag, Al:Li, or thelike); or rare earth metals such as Yb and Er can be used. In the caseof using an electron injecting layer such as LiF, CsF, CaF₂, or Li₂O, ageneral conductive thin film such as aluminum can be used. In the casewhere light is passed through the cathode 407, the cathode 407 may beformed by a lamination of an ultra thin film containing alkali metalssuch as Li or Cs and alkali earth metals such as Mg, Ca, Sr; and atransparent conductive film (such as ITO, IZO, or ZnO). Alternatively,an electron injecting layer is formed by co-evaporation of an alkalimetal or an alkali earth metal and an electron transporting material,and a transparent conductive film (such as ITO, IZO, or ZnO) may belaminated thereon to form the cathode 407.

An optical resonator is formed by two reflectors, one of which is formedto have as high reflectivity as possible and the other of which isformed to have a certain level of transmittance. Accordingly, laserlight can be emitted from the reflector that has high transmittance. Forexample, in the case where the anode 401 and the cathode 407 are used asreflectors to emit laser light, these electrodes are formed by selectingmaterials or a thickness to have transmittance of approximately from 5to 70%. Alternatively, in the case where a reflector is formedseparately, the anode 401 or cathode 407 comprise such a material thatthe light is passed through. the reflector is formed by such a materialthat light is passed through the anode 401 or the cathode 407.

The interval of the reflectors is an integral multiple of a half of thewavelength λ to be oscillated. A lamination structure of alight-emitting element is designed so that a phase of light reflected bya reflector and that of light newly generated are correspondent.

A method for laminating each layer of the above-mentioned light-emittingelement of the present invention is not limited. If the light-emittingelement can be formed by laminating layers, any method such as vacuumvapor deposition, spin coating, ink jetting, or dip coating can beutilized.

Embodiment 2

One mode of a laser oscillator including a plurality of light-emittingelements of the present invention is explained in Embodiment 2.

FIG. 6A is a top view of the laser oscillator in this embodiment when ananode of a light-emitting element is formed. FIG. 6B is across-sectional view taken along the line A-A′ of FIG. 6A. In the laseroscillator in this embodiment, a second layer 602 is formed to fillplural concave portions 600 on a first layer 601 having the pluralconcave portions 600. A reflective film 603 to be used as a reflector isformed on the second layer 602. The reflective film 603 can reflectlight emitted from a light emitting element and employ an insulatingmaterial. For example, insulating films having different refractiveindexes, such as a silicon oxide, a silicon nitride, a titanium oxidemay be alternately laminated to form a film, thereby using it as thereflective film 603.

An anode 604 is formed on the reflective film 603 to overlap the pluralconcave portions 600. The anode 604 is formed of a light-transmittingmaterial. In FIGS. 6A and 6B, the anode 604 is light-transmitting, andthe reflective film 603 is used as a reflector. However, this embodimentis not limited thereto. The anode 604 may be formed from alight-reflective material without providing the reflective film 603.

FIG. 7A is a top view of the laser oscillator in Embodiment 2 when alight-emitting element is completed. FIG. 7B is a cross-sectional viewtaken along the line A-A′ of FIG. 7A. As shown in FIGS. 7A and 7B,electroluminescent layers 605 a to 605 c corresponding to three colorsof red (R), green (G), and blue (B) are formed to overlap the pluralityof concaves 600 over the anode 604. The electroluminescent layers 605 ato 605 c are formed separately in FIG. 7A. Alternatively, theelectroluminescent layers 605 a to 605 c may be formed so as to beoverlapped partly with one another. Over the electroluminescent layers605 a to 605 c, a cathode 606 is formed to overlap the plurality ofconcaves 600.

In this embodiment, the arbitrary cathode 606 partly overlaps all ofeach anode 604. The overlapping portion serves as a light-emittingelement 607. The light-emitting elements 607 are each located in each ofthe concave portions 600. The reflective film 603 is formed to havetransmittance of approximately from 5 to 70% so that light generated inthe electroluminescent layers 605 a to 605 c is oscillated between thereflective film 603 and the cathode 606, each of which serves as areflector, to be emitted from reflective film 603. The laser lighttransmitted from the reflective film 603 is reflected by the concaveportion 600 of the first layer 601 to increase directivity. The laseroscillator of this embodiment can emit laser light from the selectedlight-emitting element 607 by controlling voltage applied to the anode604 and the cathode 606, similarly to a passive matrix light-emittingdevice.

In this embodiment, the concave portion 600 is formed to be closer tothe anode 604 than the cathode 606. Alternatively, the concave portion600 may be formed to be closer to the cathode 606 than the anode 604. Inthis instance, the anode 604 serves as the reflector and thus, is neededto be formed from a light-reflective material.

In this embodiment, the concave portion that reflects laser light andenhances the directivity is provided to overlap the light emittingelement. Alternatively, the convex portion that refract light andenhances the directivity may be provided to overlap the light emittingelement. Further, the concave portion and the convex portion may be bothprovided.

In Addition, a laser oscillator according to this embodiment may be usedas a display device. Moreover, the laser oscillator according to thisembodiment may be used as an active matrix display device by providingwith driving elements to each of light emitting elements. The displaydevice equipped with the laser oscillator according to this embodimentincludes a projector and the like.

The electroluminescent layers for R, G and B are provided in thisembodiment, but in the case of a monochrome display, oneelectroluminescent layer may be employed.

Embodiment 3

One mode of a laser oscillator shown in FIG. 8 in which a reflectivefilm that can reflect light is formed between a first layer and a secondlayer is explained in Embodiment 3.

FIG. 8 is a cross-sectional view of the laser oscillator of thisembodiment. In the laser oscillator of this embodiment as shown in FIG.8, a reflective film 802 is formed on a first layer 801 having a concaveportion 800. The reflective film 802 can be formed by a material thatcan reflect light by vapor deposition. As the material for thereflective film 802, a material containing one or a plurality of metalelements such as Al, Ag, Ti, W, Pt, or Cr can be used. The reflectivefilm 802 can be formed by a vapor deposition method. A material for thereflective film is not limited to the foregoing materials. Any materialcan be used as long as it can reflect light. For example, the reflectivefilm may be formed by stacking a plurality of insulating films, each ofwhich has different refractive indexes, such as a silicon oxide film, asilicon nitride film, and a titanium oxide film.

A second layer 803 is formed to cover the reflective film 802. Thesecond layer 803 is light-transmitting and has a thickness enough tofill the concave portion 800. Different from the mode of FIGS. 1A and1B, the refractive index of the first layer 801 is not always necessaryto be lower than that of the second layer 803 since emitted laser lightis reflected by the reflective film 802 in the laser oscillator in thisembodiment. Further, each of the first layer 801 and the second layer803 is formed by a single layer in FIG. 8, but each of the layers may beformed by a plurality of layers.

A light-emitting element 804 is formed over the second layer 803 tooverlap the concave portion 800. The light-emitting element 804 includestwo electrodes 805 and 806, and an electroluminescent layer 807interposed between the two electrodes 805 and 806. One of the electrodes805 and 806 is an anode, and the other is a cathode. FIG. 8 shows anexample that the electrode 805 serves as an anode and the electrode 806serves as a cathode. Alternatively, the electrode 805 may serve as acathode and the electrode 806 may serve as an anode. Current is suppliedto the electroluminescent layer 807 by applying a forward bias voltageto the electrodes 805 and 806, thereby making the electroluminescentlayer 807 emit light.

The first layer 801 has a curved surface in the concave portion 800. Thecenter of curvature of the curved surface is on the light emittingelement 804 side, that is, a distance of the first layer 801 to thecenter of curvature is longer than that of the first layer 801 to thelight emitting element 804.

The laser oscillator shown in FIG. 8 is provided with an opticalresonator that is formed by the electrodes 805 and 806 of thelight-emitting element 804. Light emitted from the electroluminescentlayer 807 is oscillated by the electrodes 805 and 806 to be emitted aslaser light. The optical resonator is formed so that an optical axis ofthe emitted laser light intersects with the second layer 803 and theemitted laser light is directed to the first layer 801.

Embodiment 4

A method for manufacturing a concave portion that reflects laser lightis explained in Embodiment 4. As shown in FIG. 9A, a first layer 901that is afterward provided with a concave portion is formed. The firstlayer 901 may be a glass substrate, a quartz substrate, a plasticsubstrate or the like; a resin film or an insulating film, each of whichis deposited on the foregoing substrate. Then, a mask 903 with anopening portion 902 is formed on the first layer 901.

As shown in FIG. 9B, the first layer 901 is wet-etched at the openingportion 902 of the mask 903. The wet-etching is carried out by using anetchant that is selected appropriately depending on the material of thefirst layer 901. For example, hydrofluoric acid is used as the etchantin the case where glass is used as the first layer 901. An openingportion 904 with a curved surface can be provided in the first layer 901by isotropic wet-etching.

As shown in FIG. 9C, the concave portion 906 is left in the openingportion 904 when the mask on the first layer 901 is removed. A secondlayer 905 is formed on the first layer 901 provided with the openingportion 904. The second layer 905 is formed by a material havinglight-transmitting properties to have a thickness enough to fill theconcave portion 906. The second layer 905 is formed by a material thathas higher refractive index than that of the first layer 901, forexample, transition metal oxides, nitrides, or the like can be used inthe case where the first layer 901 is mad of glass.

Although the second layer 905 is formed on the first layer 901 inEmbodiment 4, a reflective film that can reflect laser light may beformed between the first layer 901 and the second layer 905. In thisinstance, the second layer 905 may be light-transmitting, and is notrequired to be formed by a material that has higher refractive indexthan that of the first layer 901.

In the present invention, a method for manufacturing the first layer isnot limited to that explained in this embodiment.

Embodiment 5

A method for providing a convex portion in a second layer and providinga concave portion in a first layer by using the convex portion isexplained in Embodiment 5.

As shown in FIG. 10A, resin 1002 is formed, which can be melted byheating over a second layer 1001 that is afterward provided with aconvex portion. The resin 1002 is patterned to have an island-likeshape. The second layer 1001 can be a glass substrate, a quartzsubstrate, a plastic substrate, or the like.

As shown in FIG. 10B, the resin 1002 that is pattered into anisland-like shape is melted by heating so that its edge portion has acurved surface. By melting the resin 1002, resin 1003 having a curvedsurface is formed.

As shown in FIG. 10C, the second layer 1001 is dry-etched by using theresin 1003 as a mask. The dry-etching is carried out by using an etchinggas selected appropriately depending on the material of the second layer1001. For example, a fluorine gas or a chlorine gas such as CF₄, CHF₃,Cl₂, or the like can be used as the etching gas in the case that thesecond layer 1001 is made of glass. By the dry-etching, the resin 1003is etched together as shown in FIG. 10C. Lastly, a convex portion 1004can be formed in the second layer 1001 depending on the shape of theresin 1003 with a curved surface as shown in FIG. 10D.

As shown in FIG. 10E, a reflective film 1005 that can reflects laserlight is formed over the convex portion 1004 of the second layer 1001.Then, as shown in FIG. 10F, an adhesive agent 1006 that serves as afirst layer is coated on the reflective film 1005 to be adhered with asubstrate 1007. According to the structure, a concave portion can beprovided to the adhesive agent 1006 that serves as the first layer.

The reflective film 1005 is formed in order to reflect laser light inEmbodiment 5. However, laser light may be reflected by utilizing thedifference of the refractive index between the second layer 1001 and theadhesive agent 1006 that serves as the first layer. In this case, therefractive index of the adhesive agent 1006 is made lower than that ofthe second layer 1001.

Embodiment 6

One mode of an electronic device including a laser oscillator accordingto the present invention is explained in Embodiment 6.

FIG. 12A is an external view of a laser pointer including a laseroscillator of the present invention. Reference numeral 1201 denotes amain body of the laser pointer, and reference numeral 1202 denotes apackage provided with the laser oscillator therein. Internal of the mainbody 1201 is provided with a battery or the like for supplying electricpower to the package 1202. Reference numeral 1203 denotes a switch forcontrolling the application of power.

FIG. 12B is an enlarged view of the package 1202. A laser oscillator1205 is provided in a housing 1204 to shield unnecessary radiation oflaser light. A part of the housing 1204 is provided with alight-transmitting window 1207 to emit laser light from the laseroscillator 1205. The laser oscillator 1205 can be supplied with currentfrom the battery installed inside the main body 1201 via a lead 1206.

FIG. 12C is an enlarged view of the laser oscillator 1205. The laseroscillator 1205 includes a first layer 1215 with a concave portion, asecond layer 1208 formed on the first layer 1215 so as to fill theconcave portion, and a light-emitting element 1209 formed on the secondlayer 1208. The light-emitting element 1209 includes two electrodes 1210and 1211, and an electroluminescent layer 1212 interposed between thetwo electrodes 1210 and 1211. The two electrodes 1210 and 1211 areelectrically connected to a lead 1206 by a wire 1214. Reference numeral1213 corresponds to resin for sealing the electroluminescent layer 1212.The resin 1213 can prevent the electroluminescent layer 1212 from beingdeteriorated due to moisture, oxygen, or the like.

Light is generated when current is supplied to the electroluminescentlayer 1212 by applying a forward bias voltage to the electrodes 1210 and1211 via the lead 1206. Then, the light generated in theelectroluminescent layer 1212 is oscillated between the electrodes 1210and 1211, and then, the laser light is emitted from the electrode 1210side. The emitted laser light is reflected by the concave portion of thefirst layer 1215 to enhance the directivity and advances toward thelight emitting element 1209 side as shown by the arrows of broken lines.

According to the present invention, the directivity of laser lightemitted from the light emitting element 1209 can be enhanced by theconcave portion of the first layer 1215 for supporting the lightemitting element 1209. A part of the first layer 1215 serves as anoptical system, and thus, resistance to a physical impact of electronicdevices can be enhanced, which is different from the case of providingan optical system separately.

The laser oscillator having the structure illustrated in FIGS. 1A and 1Bis employed in this embodiment; however, this embodiment is not limitedto the structure. The laser oscillator shown in FIGS. 3A and 3B thatenhances the directivity by refracting laser light in a convex portionmay be used. The laser oscillator shown in FIG. 8 that is provided withthe reflective film in a concave portion of a first layer may be used.The laser oscillator shown in FIGS. 4A and 4B that can converge laserlight by using both of a concave portion and a convex portion may beused. Further, the laser oscillator shown in FIGS. 7A and 7B including aplurality of light-emitting elements formed in passive matrix form maybe used.

Embodiment 7

A structure of a light-emitting element used for a laser oscillator ofthe present invention is explained in Embodiment 7.

FIG. 13 shows one mode of a structure of a light-emitting element of thepresent invention. The light-emitting element shown in FIG. 13 has astructure including two electroluminescent layers 1303 and 1304interposed between an anode 1301 and a cathode 1302. Further, thelight-emitting element shown in FIG. 13 includes a charge generationlayer 1305, which is a floating electrode that is not connected to anexternal circuit, between the two electroluminescent layers 1303 and1304. The electroluminescent layer 1303 is formed by sequentiallystacking a hole injecting layer 1306, a hole transporting layer 1307, alight-emitting layer 1308, an electron transporting layer 1309, and anelectron injecting layer 1310 over the anode 1301. Further, theelectroluminescent layer 1304 is formed by sequentially stacking a holeinjecting layer 1315, a hole transporting layer 1311, a light-emittinglayer 1312, an electron transporting layer 1313, and an electroninjecting layer 1314 over the charge generation layer 1305.

The light-emitting element used for the laser oscillator of the presentinvention may include at least a light-emitting layer in eachelectroluminescent layer. Layers having properties other than lightemission (a hole injecting layer, a hole transporting layer, an electrontransporting layer, and an electron injecting layer) may beappropriately used with the light-emitting layer. The materials that canbe used for the layers are recited in Embodiment 1. Note that thematerials that can be used in the present invention are not limited tothose described in Embodiment 1.

When a forward bias voltage is applied to the anode 1301 and the cathode1302 of the light-emitting element shown in FIG. 13, a hole and anelectron are injected to the electroluminescent layers 1303 and 1304,respectively. Then, the recombination of carriers is carried out in eachof the electroluminescent layers 1303 and 1304 to emit light.Accordingly, in the case where the distance between the anode 1301 andthe cathode 1302 is constant, energy of light emission to be obtained atthe same amount of current becomes higher than in the case where alight-emitting element includes only one electroluminescent layer.Therefore, emission efficiency of laser light can be improved.

The charge generation layer 1305 may be formed by a material that cantransmit light. For example, an ITO, a mixture of, V₂O₅ and an arylaminederivative; a mixture of MoO₃ and an arylamine derivative; a mixture ofV₂O₅ and F4TCNQ (tetrafluoro tetrathiafulvalene); and the like can beused.

When the anode 1301 and the cathode 1302 are used as reflectors,materials or thickness thereof are selected so that the reflectance ofone of these electrodes is as high as possible and the transmittance ofthe other electrode is approximately 5 to 70%. In the case where areflector is formed separately, the anode 1301 or cathode 1302 comprisesuch a material that the light is passed through. Further, the distancebetween reflectors is an integral multiple of a half of the wavelength λto be oscillated. A lamination structure of a light-emitting element isdesigned, so that light reflected by a reflector and a phase of newlygenerated light are correspondent.

Embodiment 8

A shape of a concave portion of the laser oscillator of the presentinvention is described in Embodiment 8.

FIG. 14 shows a positional relationship of a layer 1501 (a reflectivefilm, here) having a concave portion 1500 to reflect light and a laserlight-source 1502. The laser light-source 1502 includes an opticalresonator and a laser medium, in which laser light is emitted toward theconcave portion 1500 from the laser light-source 1502. The concaveportion 1500 has a center of curvature O′ on the laser light-source 1502side.

The laser light-source 1502 is a surface light-source having a certaindegree of area enough to emit laser light. The laser light emitted fromthe surface light-source has a divergence angle θ. Herein, it issupposed that a point light-source having a divergence angle θ islocated at a focal point O and light emitted from the laser light-source1502 diverges similarly to light emitted from the point light-source. Inthis case, the highest directivity of the laser light which is reflectedby the concave portion 1500 can be obtained by adjusting the focal pointO on the center of curvature O′ side of the concave portion 1500 to thepoint light-source.

Therefore, the focus length of the concave portion 1500 is denoted by f,the width of the laser light-source 1502 is denoted by 2t, and thedistance between the laser light-source 1502 and the concave portion1500 is denoted by Y. When the relation of the divergence angle θ andthe focus length f is expressed by the next equation (Equation 1), it isconsidered that the highest directivity of laser light reflected by theconcave portion 1500 can be obtained at this time.

$\begin{matrix}{f = {Y + {t\sqrt{\frac{1}{\sin^{2}\theta} - 1}}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

Note that the focus length f is equivalent to a half of the radius ofcurvature R, and thus, the next equation (Equation 2) can be obtainedfrom the equation 1.

$\begin{matrix}{R = {2 \times \left( {Y + {t\sqrt{\frac{1}{\sin^{2}\theta} - 1}}} \right)}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

The shape of the concave portion 1500 can be optically designed toenhance the directivity of laser light by using Equation 1 or Equation2.

In Addition, a laser oscillator according to the invention may be usedas a display device. The display device equipped with the laseroscillator includes a projector, LCD (Liquid crystal display), using thelaser oscillator as a backlight, and the like. Specifically, in the caseof FS-LCD (Field sequential LCD), a light emitting element shown inembodiment 2 that has electroluminescent layers corresponding to each ofR, Q and B may be used. As an example of the FS-LCD, the entiredisclosure of US Patent 2003/0058210 is incorporated herein byreference.

This application is based on Japanese Patent Application serial no.2003-322287 filed in Japan Patent Office on Sep. 12, 2003, the contentsof which are hereby incorporated by reference.

Although the present invention has been fully described by way ofEmbodiment Mode and Embodiments with reference to the accompanyingdrawings, it is to be understood that various changes and modificationswill be apparent to those skilled in the art. Therefore, unless suchchanges and modifications depart from the scope of the present inventionhereinafter defined, they should be constructed as being includedtherein.

What is claimed is:
 1. A device comprising: a first layer over asubstrate; a light emitting element over the first layer; and a secondlayer that is light-transmitting and that is formed to cover the lightemitting element, wherein the second layer has a curved convex portionwhich overlaps with the light emitting element.
 2. The device accordingto claim 1, wherein the light emitting element comprises: a firstelectrode over the first layer; a first organic electroluminescent layerover the first electrode; a second organic electroluminescent layer overthe first organic electroluminescent layer; a charge generation layerbetween the first and the second organic electroluminescent layers; anda second electrode over the second organic electroluminescent layer. 3.The device according to claim 2, wherein the charge generation layercomprises molybdenum oxide.
 4. The device according to claim 1, whereinthe device is a laser oscillator.
 5. The device according to claim 1,wherein the substrate is an insulating substrate.
 6. A display devicecomprising a backlight including the device according to claim
 1. 7. Adevice comprising: a first layer over a substrate; a plurality of lightemitting elements arranged in a matrix over the first layer; and asecond layer that is light-transmitting and that is formed to cover theplurality of light emitting elements, wherein the second layer has aplurality of curved convex portions, each curved convex portionoverlapping one of the plurality of light emitting elements.
 8. Thedevice according to claim 7, wherein each of the plurality of lightemitting elements comprises: a first electrode over the first layer; afirst organic electroluminescent layer over the first electrode; asecond organic electroluminescent layer over the first organicelectroluminescent layer; a charge generation layer between the firstand the second organic electroluminescent layers; and a second electrodeover the second organic electroluminescent layer.
 9. The deviceaccording to claim 8, wherein the charge generation layer comprisesmolybdenum oxide.
 10. The device according to claim 7, wherein thedevice is a laser oscillator.
 11. The device according to claim 7,wherein the substrate is an insulating substrate.
 12. A display devicecomprising a backlight including the device according to claim
 7. 13. Adevice comprising: a first layer over a substrate; a light emittingelement over the first layer; a second layer that is light-transmittingand that is formed to cover the light emitting element; and a thirdlayer between the first layer and the light emitting element, whereinthe second layer has a curved convex portion which overlaps with thelight emitting element.
 14. The device according to claim 13, whereinthe light emitting element comprises: a first electrode over the firstlayer; a first organic electroluminescent layer over the firstelectrode; a second organic electroluminescent layer over the firstorganic electroluminescent layer; a charge generation layer between thefirst and the second organic electroluminescent layers; and a secondelectrode over the second organic electroluminescent layer.
 15. Thedevice according to claim 14, wherein the charge generation layercomprises molybdenum oxide.
 16. The device according to claim 13,wherein a refractive index of the first layer is lower than a refractiveindex of the third layer.
 17. The device according to claim 13, furthercomprising a reflective film between the first layer and the thirdlayer.
 18. The device according to claim 13, wherein the device is alaser oscillator.
 19. The device according to claim 13, wherein thesubstrate is an insulating substrate.
 20. A display device comprising abacklight including the device according to claim
 13. 21. A devicecomprising: a first layer over a substrate; a plurality of lightemitting elements arranged in a matrix over the first layer; a secondlayer that is light-transmitting and that is formed to cover theplurality of light emitting elements, and a third layer between thefirst layer and the plurality of light emitting elements, wherein thesecond layer has a plurality of curved convex portions, each curvedconvex portion overlapping one of the plurality of light emittingelements.
 22. The device according to claim 21, wherein each of theplurality of light emitting elements comprises: a first electrode overthe first layer; a first organic electroluminescent layer over the firstelectrode; a second organic electroluminescent layer over the firstorganic electroluminescent layer; a charge generation layer between thefirst and the second organic electroluminescent layers; and a secondelectrode over the second organic electroluminescent layer.
 23. Thedevice according to claim 22, wherein the charge generation layercomprises molybdenum oxide.
 24. The device according to claim 21,wherein a refractive index of the first layer is lower than a refractiveindex of the third layer.
 25. The device according to claim 21, furthercomprising a reflective film between the first layer and the thirdlayer.
 26. The device according to claim 21, wherein the device is alaser oscillator.
 27. The device according to claim 21, wherein thesubstrate is an insulating substrate.
 28. A display device comprising abacklight including the device according to claim 21.